406sbc for 1/4 mile dirt need suggestions

Building a 400sbc .030'' over for a pure stock class.I need suggestions on parts to build it with.Keep in mind my rules state i must use stock gm heads,cast iron intake,idle smooth,& pull 17''of vacume @ 1000rpm. Heads::??I have 2 sets.One set of 461 double humps 62cc & then a 487 & a 487x 75cc.Anybody know the difference between the 487 & 487x ? Pistons::Have a set of new cast domed."A lot like flat tops with 2 valve reliefs but 1/3 of the top has a 1/16'' rise.When i bought them 20 yrs ago i was told that with 76cc heads these would be about 9.7:1 compression. I am thinking about buying a new set of forged pistons with new rods,but 5.7'' or 6.0''??.{from speedway catalog}. CAM??LIFTERS??ROCKERS??. Thinking about going with a cam & lifter combo from speedway also. Remember the 17'' vac rule. Don't exspect to get over 5000rpm. Plan on modifying a hei as per a wiki article & have a new elderbrock 600cfm 4 barrel carb. I know the 461 heads may make the comp way high with the pistons i have now.I do plan on using fuel additive,or some,or all racing gas. Main thing now guys is what to use to get the long block built.?? NO Dummy::I have 25yrs in CAT gas & diesel engines,just now getting to race a little.ANY help appreciated!


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3973487....71-72...350..........1.94/1.5 or 2.02/1.6 valves, was also used on '71 350/330hp LT1, 75cc chamber
3973487X...71-72...350..........1.94/1.5 or 2.02/1.6 valves, 75cc chamber

Give us a call at 931-762-3977. We have winning vacum rule cam for stock class that will help you turn more rpm with more torque over stock cam. Some customer say our cam will pull high as 20" of vacum in their engine.

If you don't have a compression limit put all the squeeze to her it will handle, use race fuel only.With your limited induction compression will really help the power don't be afraid to spin it a little more. contact a cam grinder for compression recomendations as the smooth idle rule is the limiter the compression will help the vacuum situation.As far as heads either will work well but the humps can use a smaller dome which will help flame travel.

I would use an intake like the one shown below (was for sale for $100 HERE.) and a set of Vortec heads. Your domed pistons won't be a good match, but if you're thinking about new pistons anyway...

The Vortec's will slay either head you have now.

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Thanks ! sounds like some solid advice.my pistons don't have a dome but more of a ledge.I got a reply from a cam guy also i plan on contacting.

what years ,models ect am i looking for for the vortec heads i keep hearing about? The double humps were the hottest thing back in my day 25 yrs ago before a family & work.Fill me up with info guys!

I seen a good trick from a pro engine builder on the 400s for gasket and upper ring cylinder seal and this is what I'm doing on my 400 that is putting in deck plugs to sure the deck surface. I don't know if this will help in your case or not I did it cause I'm using aluminum heads on mine but we'll see. Good luck though !

to red 69 nova::not clear on what you call deck plugs.What i am invissioning is like a diesel cly sleve counter bore.Don't think i will go that extreem but would like to clear up what ya mean.I have also put inserts on diesel blocks for the water passages.

for the vortec heads 96 and later chevy pickups they have centerbolt valve covers but be carefull what your buying just cause they have center bolt valve covers dont mean they are vortec heads alot of people will try and sell you some crappy stuff as good stuff around here anyway

With vortecs you will need a flat top piston as a dome generaly won't clear the chamber.Also check rules because there are no stock cast iron intakes for them.

There are cast iron GM intakes w/GM part numbers. Used on boats. See the photo/link above for more.

Depending on the interpretation of the rules, this intake may or may not be legal. All it takes is a phone call to the sanctioning body to find out.

Do a search using "vortec heads" and you will get dozens of threads talking all about them.

The short story is they outflow any SBC cast iron head GM made previously for mass consumption, including double hump/fulie and Bowtie heads.

This is true cobalt with one exeption you have to rember stock flow numbers on the bowtie mean nothing.They were designed with a lot of extra meat in the port areas in anticipation that anyone using them would be in a class where porting was legal.They were basicaly a blank sheet to start with so you could port them for your needs a vortec wouldn't stand a chance against properly ported bowties.The old 292 turbos that the bowties replaced could pull 750 hp in prostock form and 600 in cup trim(no welding or extensive porting due to durability concerns).

My comment, was based on having to use production iron heads- like the heads he mentioned- and like are required for many/most cast iron head and intake "hobby stock" or entry-level classes.

Like I said, it depends on the rules and the interpretation of them.

I would hope the OP doesn't hope to use the heads he mentioned in a class that allows ported non-production cylinder heads. In that case I still wouldn't use bowtie heads, there are better raw material out there for unlimited cast iron heads, IMO.

But the Vortec's will be better than either head he mentions or any head Chevy makes- if an as-cast production-based cast iron head is spec'ed AND the cast iron GM boat intake is deemed to be legal.

I hope this clarifies things a little.

Late hopper upper, just what are your rules you have to "abide" by?

I agree on the as cast part.However in 20 something years of dirt tracking I have rarely seen tech guys who can find good undercover porting.Some tracks and associations have them but most don't. This is where acid porting and reblasting the ports comes in.It would be nice if everybody played by the rules but the simple truth is most circle trackers look at the rules as a suggestion not a law.The old saying in this sport is "If you ain't cheating you ain't competing"